Basically, the game consists of listing words related to a topic. Each word must either START or END in a key letter. Look at the graphic below to make this clear. You'll notice that every line has at least one shaded circle. A letter written in those shaded circles are the key letters for the word to be written in the next line. If a word passes through two shaded circles, then the player has a choice as to which letter he or she uses as the key letter for the next word.
(from website)

Full Game: http://www.gamecabinet.com/rules/StartsAndEnds.html